Multiple patterning lithography (MPL) uses multiple masks to print layout geometries when forming a semiconductor device. Respective masks comprise one or more holes or transparencies that allow light to shine through in a defined pattern. The pattern of light is directed onto an underlying layer to form polygons of a layout geometry at least one of in, on, or from the underlying layer.
Mask loading refers to a distribution of holes across the multiple masks in MPL. An uneven distribution, also referred to as an unbalanced mask loading, refers to a situation where a total area of holes in a first mask is disproportionate to a total area of holes in a second mask such that a total area of polygons formed by the first mask is disproportionate to a total area of polygons formed by the second mask. Such uneven distribution is associated with process variation and a low yield, for example.